Gas turbines are used in many fields, for driving generators or working machines. In this case, the energy content of a fuel is used to produce a rotary movement of a turbine shaft. The fuel is for this purpose burnt in a combustion chamber, with compressed air being supplied from an air compressor. The working medium which is produced by the combustion of the fuel in the combustion chamber and is at high pressure and high temperature is in this case passed via a turbine unit, which is connected downstream from the combustion chamber and where it is expanded producing work.
In this case, in order to produce the rotary movement of the turbine shaft, a number of rotor blades are arranged on the turbine shaft, are normally combined to form blade groups or blade rows and drive the turbine shaft via the impulse which is transmitted from the working medium. Furthermore, stator blades, which are normally connected to the turbine housing between adjacent stator blade rows and are combined to form stator blade rows, are normally provided to guide the flow of the working medium. These stator blades are attached to a normally hollow-cylindrical or hollow-conical stator blade support.
When designing gas turbines such as these, in addition to the power which can be achieved, particularly high efficiency is normally a design aim. In this case, for thermodynamic reasons, the efficiency can in principle be increased by increasing the outlet temperature at which the working medium flows out of the combustion chamber and into the turbine unit. In this case, temperatures of about 1200° C. to 1500° C. are both desired and achieved for gas turbines such as these.
However, when the working medium is at high temperatures such as these, the components and parts which are subject to these temperatures are subject to high thermal loads. The hot gas channel is normally clad by so-called annular segments, which form axial sections of the outer wall of the hot gas channel. These are normally attached via hook elements to the stator blade support, as a result of which the totality of the annular segments in the circumferential direction, in the same way as the stator blade support, forms a hollow-conical or hollow-cylindrical structure.
The components of the gas turbine can be deformed by different thermal expansion in different operating states, and this has a direct influence on the size of the radial gaps between the rotor blades and the outer wall of the hot gas channel. These radial gaps may be of different size while the turbine is being run up and shut down than during normal operation. When designing the gas turbine, components such as the stator blade support or outer wall must always be designed such that the radial gaps are kept sufficiently large to prevent the gas turbine from being damaged in any operating state. However, a correspondingly comparatively generous design of the radial gaps leads to considerable efficiency losses.
In order to overcome this problem, JP 2005-042612 proposes that the stator blade support being designed such that it can be cooled, with the aim of reducing the thermally dependent deformation. According to JP 54-081409, this problem is intended to be solved by a plurality of gas bleed chambers, which leads to uniform stiffness of the upper and lower housing part.